From the dashboard
Your dashboard always shows the balance due from your clients
You can click those widgets to see a list of clients with due balances
From the clients list
You can view your balances with client on your clients section form the left menu.
Clicking on the due balance widget or past due widget
Will show you a list of only clients with balances.
From the invoices report
You can click the invoices page from the left menu.
Here you can view invoices by their paid status and by date range.